The present invention relates to a rotational airfoil assembly, and more particularly to a balance system therefor.
Aircraft such as turboprops, tilt rotors and helicopters include rotational airfoil assemblies such as propeller blade and rotor blade systems. Propeller blades are secured to a hub of an aircraft via a retention assembly. The blades are dynamically balanced about the axis of rotation of the hub to minimize vibration and noise that may occur during operation. Specifically, the blades must be balanced about the axis of rotation of the hub to balance both the action of a centrifugal force produced by the rotation of the blades and the moments caused by aerodynamic forces generated by the relative speed of the blades with respect to the air.
One conventional method of blade balancing includes machining a cavity into a blade on an inboard side of the blade and inserting lead wool into the machined cavity until the proper balance is achieved. Disadvantageously, blade balance systems of this type are relatively expensive to manufacture due the relatively large amount of machining required to provide the cavity within the blade bore.
Other conventional blade balance systems include a removable balance cartridge insertable into a bore of a blade. A receiver is bonded to the bore of the blade on an inboard side the blade and a balance cartridge is mounted within the receiver. The balance requirements of each particular blade are determined by balancing the blade against a pre-balanced master blade on a balance stand. Once the balance requirement is determined for a particular blade, an appropriate number of relatively high density weights are mounted within the balance cartridge to provide the necessary balance.
Although effective, conventional blade balance systems require a relatively significant quantity of weight to be added relative to the overall weight of a blade.
Accordingly, it is desirable to provide a balance system for a rotational airfoil that effectively balances a rotational airfoil with a minimal addition to the overall blade weight.